Hi again, Scott,
Glad to hear that you've given yourselves an extra day.
As far as things to see and do along the way, there are many, some involving scenic side road drives. As you're not planning to drive all the way through to Scrabster, you'll have more time to drive and enjoy.
As you leave Skye on the A87, you have the option of taking the side roads for Drumbuie, Duirinish, and Plockton. There are Highland cows in the roadway at Duirinish, and Plockton is one of the most charming villages in the Highlands. You can cut across to the A890 from there, along the shore of Loch Carron.
If you don't go that way, you have the option of visiting the Lochalsh Woodland Garden about three miles along the A87. There is a circular walk that takes you through some lovely woods and plantings, with views over Loch Alsh.
There are magnificent views across Loch Carron from the top of the A890. Once you get to Lochcarron village, check out the athletic field at the west end of the village to see if there might be a shinty match going on. There is a self serve car wash at the garage in Lochcarron, if your car needs a hosing down. It may be the only car wash west of Inverness.
Stay on the A896 for a few miles to the turn off for the Bealach-na-Ba, which is the road to Applecross. The view from the top, back over Loch Kishorn and Loch Carron, is absolutely stunning. Once you arrive in Applecross (toilets at the campsite), follow the coastal road to Shieldaig.
Once you're back on the A896, follow it through Glen Torridon, through the Beinn Eighe Nature Reserve. You have the option of a short hike in the area of Liathach.
At Kinlochewe, turn left on the A832 for Gairloch, which is a good place to stop for a meal. If you are beach people, the beach and dunes at Big Sand are worth a brief stop. Heading north from Gairloch, the next village is Poolewe, where you'll find the excellent Inverewe Gardens.
The A832 loops around Gruinard Bay and Little Loch Broom, and meets up with the A835 at Braemore. Take a few minutes to walk down to the bridge over the Corrieshalloch Gorge and waterfall. Head north on the A835 for Ullapool.
After Ullapool, you have a couple of options. At Drumrunie Lodge, you can turn left on the unclassified road for Achiltibuie and Loch Lurgainn. Stac Pollaidh is the uniquely shaped mountain on the right as you pass Loch Lurgainn. Don't go all the way to Achiltibuie, but instead, take the unclassified road on the right just past the end of Loch Lurgainn. This is the "Wee Mad Road," and will take you to Lochinver.
If you don't have time to detour via Loch Lurgainn, keep going up the A835 to Ledmore Junction, where you'll turn left on the A837. Stay on the A837 to Lochinver.
After you reach Lochinver, follow the B869 through Stoer and Drumbeg. This is a road not to be missed!
The B869 ends at the A894, which you'll follow north to the village of Scourie. If you get there around sunset, and it looks as though it will be a good one, a short side trip to the hamlet of Badcall would be a great place to see the sun dipping below the horizon. Scourie would be a good place for an overnight, unless you plan to push on to Durness, which is another 25 miles up the road.
From Scourie, the A894 takes you to Laxford Bridge, where you'll meet up with the A838 for Durness. If you're not pressed for time, a side trip to Kinlochbervie might be worth your time, and if you have about six hours to spare, the hike out to Sandwood Bay is well worth it. The path starts from near Oldshoremore, and Sandwood Bay has the most spectacular beach on the Scottish mainland.
From Durness (Balnakeil Bay is worth a visit), you'll head across the top of the mainland for Thurso and Durness. Much of the scenery is bleak and barren, but beautiful in its own way. Give yourselves plenty of time to get to Thurso and Scrabster, as there are no fast roads.